Passive monitoring of Voice over Internet Protocol (VoIP) calls is a way of measuring network performance and troubleshooting signaling problems in a network. This monitoring preferably needs visibility into all messages in call signaling transactions. However, it is common that at any point in the network only part of the signaling flow is visible. It is also likely that monitoring complete VoIP transactions is not possible due to the in-deterministic routing nature of the internet protocol (IP) and requires deployment of multiple monitoring probes in the network. Generally, in order to measure network and call quality completely, information for the entire call must be gathered from each device and correlated at a central location.
There are several different possibilities for the choice of this central location. First, a central server could be used. However, this solution is not scalable since many thousands of calls may be detected across a multitude of monitoring devices throughout the network. Second, the monitoring devices could be organized into groups, where information pertaining to each partial call detected by a member of the group is shared with all other group members. This method wastes network bandwidth, and does not allow monitoring when a call is seen by devices belonging to different groups. Thus, a need exists to improve correlating network transactions in this technology field.